286 EXPERIMENT STATION EECORD. [Vol.36 



compound footings, piles, retaining walls, culverts, girder bridges, concrete 

 building blocks, fence posts, silos, concrete walks, concrete curb, concrete 

 construction work, and flat-slab construction. 



Calcium chlorid hastens seasoning of concrete (Engin. Rec, 74 {1916), No. 

 9, pp. 266, 261, figs. 3).— Tests conducted at the U. S. Bureau of Standards, 

 under the supervision of R. J. Wig, of the 1 : 3 standard sand mortar showed 

 that the rate of hardening was accelerated by the addition of calcium chlorid. 

 It also increased the strength at 24 hours by from 155 to 230 per cent and at 

 48 hours by from 173 to 190 per cent over the strength of mortar containing no 

 calcium chlorid. The best percentage of calcium chlorid to use for all propor- 

 tions of concrete was from 3 to 4 per cent of the weight of the mixing water. 

 The increase in strength at 48 hours thus obtained varied from 14 to 275 per 

 cent for the 1:2:4 mix and from 11 to 110 per cent for the 1 : 1.5 : 3 mix. 

 In all but one case the concretes mixed with 4 per cent of calcium chlorid 

 showed a greater sti'ength for both mixes than for plain concrete, these results 

 being consistent, though variable, for all the ages tested up to 30 days. This 

 acceleration in strength is believed to be due to the more complete hydration 

 of the silicates and aluminates in the setting of the cement. 



" The use of calcium chlorid increases the cost of concrete by 12 to 15 cts. 

 per cubic yard. For best results it is important that the concrete be mixed to 

 a quaking, but not fluid, consistency. Calcium chlorid should be used with 

 caution for reinforced concrete construction, as it tends to accelerate any 

 corrosion of the steel which may occur." 



Tensile strength of Portland cement mortars containing lime, M. O. Fuller 

 {Concrete [Detroit, Mich.], 9 {1916), No. 3, pp. S9-91, figs. 7).— Nine series of 

 tests of the tensile strength of Portland cement mortars with and without 

 hydrated lime are reported. Cement paste and 1 : 3 mortar of both normal 

 and working consistencies and 1 : 3 mortar of working consistency containing 

 2:5, 5, 7.5, and 10 per cent of hydrated lime were tested after storage under 

 water, in laboratory air, outdoors exposed to the elements, in air and water, and 

 in moist clayey soil. 



It was found that " so far as specimens stored under water or in ground 

 are concerned, the presence of lime increases the tensile strength. As compared 

 with the above two kinds of storage ... a storage of test specimens in dry 

 air shows that for 21 days mortar containing no lime developed the greater 

 strength. After 21 days the mortars containing lime showed an increase in 

 strength, while those containing no hydrate decreased or remained nearly con- 

 stant. . . . An addition of hydrated lime up to 10 per cent of the cement not 

 only increases very considerably the plasticity of the mortar but also increases 

 the tensile sti-ength." 



The economical brick mortar {Cement and Engin. Neics, 28 {1916), No. 9, 

 pp. 192, 193). — Experiments conducted by J. S. Macgregor at Columbia Uni- 

 versity with seven different sets of nine piers, 8 by 8 by 84 in., constructed 

 of hard-burned face bricks and common bricks bound with cement mortars of 

 different proportions and containing varying amounts of hydrated lime, are 

 reported, the purpose being to determine to what extent hydrated lime may 

 replace cement in the mortar without reducing the factor of safety under 

 practical conditions. The results are shown in the following table: 



